/sys$common/syshlp/helplib.hlb PASCAL, Expressions, Operators, Logical Operators  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  A logical operator evaluates one or more Boolean expressions and
  returns a Boolean value.

  Logical Operators:

     operator    |  example       |    result
     -------------------------------------------------
       AND           A AND B         TRUE if both A and B are TRUE

       OR            A OR B          TRUE if either A or B is TRUE,
                                     or if both are TRUE

       NOT           NOT A           TRUE if A is FALSE, and
                                     FALSE if A is TRUE

       AND_THEN      A AND_THEN B    TRUE if both A and B are TRUE
                                     (forces left-to-right evaluation
                                      order with short-circuiting)

       OR_ELSE       A OR_ELSE B     TRUE if either A or B is TRUE,
                                     or if both are TRUE
                                     (forces left-to-right evaluation
                                      order with short-circuiting)